Wednesday, 28 March 2018

BSA A10


The machine was purchased locally. It had been standing in a barn for quite a long time. When I first saw it, I thought 'this looks good'. The chap who was selling the bike told me it was the last one of a few British bikes that he had owned and the reason for the sale was that he was going Formula Ford racing! With rear-sets, clip-ons, alloy wheels and TT100 tyres it really looked the business. I had already decided in my own mind that this motorcycle was going to be mine.

As the plug leads had been removed for security reasons I agreed to buy the bike if I could hear the engine run. After looking around the barn we failed to find any leads, so I decided to return the following evening to attempt to start it. Taking two friends along we attached the leads to the magneto, tickled the carb and after a couple of hopeful kicks she fired up. I had to try not to look too happy as a final price had still not been agreed. Still, it did sound very nice gurgling away in this old stone barn.

After some good old Yorkshire bullshitting had taken place, from both sides, I agreed on seven hundred quid. We loaded her into Mick's van and took her home. That was the easy part! How the hell can a mere working man explain to the female equivalent of Bamber Gascoigne the logic in spending the new carpet money on another bike? After the usual arguments I assured my wife that this bike was really a good investment, a 1958 BSA A10 650cc vertical twin could hardly be anything else, could it?

By. the end of the fifties, the A10 was in reasonable shape. Its pre-unit engine was as reliable as anything else available from the British industry, its handling was better than the Triumphs, but not quite up to the standard of the Nortons, and if outright performance could not really match its rivals, they were reputed to have better longevity. The A10 also looked a lot more butch than the later, unit A65.

I started off by washing off all the dust and dirt, which made the bike look even better (talk about beauty in the eye of the beholder). Next I emptied all the old oil and cleaned out the oil tank filter. In with the new oil, adjust the brakes, tighten various nuts and bolts, then we were just about ready to go. On with the black gear, start her up and off on the maiden trip Seemed okay, so far so good.

After a few miles I began to notice my left hand was becoming tired, the bloody clutch was dragging and felt like hell. The engine started to become harsher, my arms started to tire and my forty year old back had started to react to the riding position resulting from the clip-ons and rear-sets.

The suspension was typical of these old British twins, short of movement and harsh of action, it did little to cushion my body from the bumpy road surface. God knows what it would've been like if, instead of the conventional swinging arm and twin shocks, it had an earlier plunger frame.

I started to work my way home, the pain that was running through my body was becoming distracting to the extent that l was finding it hard to keep the bike on the move and upright. I managed to make it home, riding straight into the garage, I stopped the engine, leaning the bars against the wall. I slid off the damned thing on to the floor.

How the hell did the blokes in the sixties ride six laps around the IOM on these things? After three or four days I returned to the garage... l could nearly walk straight again. Looking at the BSA I realised it needed drastic alterations, so off came the clip-ons and rear-sets in favour of the standard gear that came as spares with the bike. Sitting on the bike it felt much better.

After giving the bike a look over I found the engine mounting bolts were a bit loose. I nipped them up and once again set off on a run around the village. This time things were a lot better, I did about ten miles and returned home. The only real problem I encountered was remembering to leave sufficient braking room to compensate for the ancient SLS drum brakes.

I once again checked the bike over... yes, the engine mounting bolts were loose again. I began to wonder why? Was there something amiss within the motor. After studying the ubiquitous Haynes manual I was not much wiser. I decided to investigate by removing the timing cover... I had a double dose of excess crank end float and lift.

I have since learnt that this is a common fault on BSA twins, so much so that SRM managed to make a good business out of doing a roller bearing conversion for the crankshaft. Deciding to do something about it, I promptly took out the engine and stripped it. I found the main bush was well worn, the big-ends were on their way out, so new shells were ordered plus a gasket set. I was lucky to find a serviceable main bush in some crankcases a friend had donated to the cause. On rebuilding the motor I used plenty of Loctite to hold everything together. One good thing about British stuff, it can all be torn apart and thrown together with a minimum of knowledge and special tools.

The rebuild was completed in a couple of days and I took the bike out for a slow run. After only a couple of miles the engine just didn’t feel right so I turned the bike around, hoping to make it back home in one piece. With half a mile left there was a loud bang... the left hand con-rod had made a break for freedom. Leaving the bike I walked away cursing myself, what the hell had I done wrong?

After using a friend’s phone to summon a rescue squad, I returned to the bike to find some lout all over my pride and joy. He claimed the bike had been abandoned and only reluctantly did a disappearing act when I pointed out the engine was still hot. After the tow home the motor was pulled out and stripped... the crank was scrap due to the large hole left by the conrod.

The seizure had been all my fault, when l assembled the main bearings I had used copious quantities of Loctite to stop them rotating, some of the Loctite had run into the oil feed, thus cutting off the supply of lubricant to the bottom end. The necessary spares were found in the usual way, through friends who also ran British bikes. I ended up with a big bearing crank with conrods to match, which I had balanced.

Another problem was worn out pistons, which were plus 60, so new barrels or liners were needed. £35 for a pair of Empire Star pistons solved that particular problem, although various old codgers were a bit horrified when l revealed that the barrels had been bored out to 72mm to suit. The piston skirts need 5mm taken off to avoid the pistons hitting the flywheel, by the way. A new SRM barrel costs £225, which was too much for me. It's very important to get the piston to bore clearance dead right, I have found that 5/6th thou is about right if you like to motor on a bit.

Which brings me to performance. Obviously, a late fifties machine will have trouble keeping up with big Japs and even some 250s will burn it off. That's to miss the point, as the way the venerable twin delivers its power is a delight. I usually ride in the company of other British bikes and it keeps up with things like Super Rockets. It really amazes me how good a bike it is to ride, although it really pisses me off that I’ve had to play about so much with mine. Handling is not at all bad, at least it feels just as secure in the wet as in the dry, unlike many a Jap machine, and given the limits of performance and its age, it can still motor along like a good 'un.

That's pretty typical of British bikes in this price range. It's very easy to become all nostalgic when you see these big twins, with their brutal appearance and shiny chrome, but as I found out, it's all too easy to buy one that whilst it appears to run OK hides all kind of maladies internally. Still that's all in the past now... the ferry sailings for the IOM are confirmed!

Chris Hunt

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